I hope you are talking epoxy paint? I wouldn't paint a plane and then put a layer of epoxy on it. Huge weight and nothing else gained. If you are going to paint, prime and paint, that is the protection, if you are going to cover, just cover. The covering is the protection. I don't understand the painting and then epoxy over the top. I have never seen that done. Doesn't sound like a good way to do it. Maybe I missed what you are saying, I hope.